Underfeed stoker grate



March 24, 1936. F. L. HITCHCOCK UNDERFEED STOKER GRATE Filed May 14, 1934 3 Sheets-Sheet l Inv enLov For H? 3L L. Hitchcock,

ALLoYnegs arch 1936- F. HITCHCOCK UNDERF'EED STOKER G ATE Filed May 14, 1934 3 Sheets-Sheet 2 lklal.

Inventor Fonesb LHiLchc'och Patented Mar. 24, 1936 2,035,128 UNDERFEED s'roKEn GRATE Forrest L. Hitchcock, Indianapolis, Ind., assignor to Furnaslave, Inc.

ApplicationMay 14, 1934, Serial No. 725,557

8 Claims. ((1110-45) This invention relates to the art of stokers and particularly to a grate bar structure to be used in an under-feeding stoker. An important object of the invention is to provide a grate structure which will not only aid in preventing the coking over of fuels thereon but will also cause ashes to sift down therethrough and to grind clinkers into small particles which will pass between the bars of the grate.

An important object of the invention is to provide a grate structure wherein individual bars will have a longitudinal shearing action one past the other so as to effect a crushing or grinding action on particles becoming engaged therebetween.

Another important object of the invention is to provide a grate structure which will receive fuel centrally therethrough and cause the fuel to spread outwardly to promote a fire bed extending to the outermost part of the grate structure. A still further important object of the invention is to so shape the grate bars that upon being shifted; the ashes and clinkers resulting from the combustion of the fuel will be worked outwardly from the center thereof so as to bring the larger particles in particular in the ashes to those zones over the bars wherein the maximum shearing action therebetween takes place. a

These and other objects and advantages wil become apparent to those skilled in the art in the following description of one particular form of the invention as illustrated by the accompanying drawings, in which Fig. 1 is a fragmentary top plan view of a structure embodying my invention;

Fig. 2, a fragmentary central longitudinal verticalsection through the structure; I

Fig. 3, a'detail in top plan view of a pair of grate bars in shifted positions;

Fig. 4,;a section on the line 4-4 in Fig. 3;

Fig. 53a top plan view of an elongated grate structure;"

Fig. 6, a detail in vermin section on the line Fig.7, a detail in top plan view of the filler ring; and

Fig. 8, a detail in section on the line 8-8 in Fig. 7.

Like characters of reference indicate like parts throughout the several views in the drawings.

I employ a fuel conducting tube or pipe III which is supported by its inner endwlthin a furnace to which the device is to be applied by a foot II which carries an adjustable leg l2 to extend downwardly and bear on the floor. inner end of the pipe l0 turns upwardly to carry a sleeve IS in fixed relation thereto. This sleeve has an internal diameter corresponding to that of the upturned end of the pipe Ill so as to in effect form a continuation thereof. Toward the The upper end of the sleeve I3 is provided a flange 14 extending horizontally therefrom. This flange I4 is provided with a plurality of openings I5 to permit the passage of air upwardly therethrough externally of the sleeve I3. The outer edge of the flange I4 is formed to have a step extending therearound on which is revolubly received a plate It, the plate being mounted thereby centrally of the sleeve 4 l3. Preferably the plate I6 is provided with a Cylindrical depending skirt I! from which braces I8 extend upwardly and outwardly to the under side of the plate l6 as a means of reenforcing it to prevent warping.

This skirt I1 is open from the under side so that air may pass up therethrough to discharge through the holes [5. The plate I6 is provided with a plurality o openings [9 therethrough so as to provide for PATENT OFFICE".

the passage of air through the plate externally of the skirt ll. 0n the top side of the plate l6 are carried a plurality of pins 2!] equally spaced apart around a common circumference near the periphery of the plate. A collar 2| engages over the upper end of the sleeve l3 to rest on the flange l4 and extend upwardly therefrom. This collar 2! has an outwardly extending annular flange 22 at its upper end, in which flange are provided a. plurality of holes 23. The number of holes 23 correspond to the number of pins 20.

I provide a plurality of individual grate bars- 24, two only being shown in Fig. 1 for the sake of clearness. Each of these bars 24 has a more or less triangular shape in top plan view with a substantially arcuate vertical cross section. The inner end of the bar is provided with a pin 25 extending vertically downwardly therefrom to pass through a hole 23 in the flange 22 and preferably a foot or lug 26 extends from one side of the pin 25 horizontally to engage against the under side of the flange 22 toward the sleeve 2| whereby the inner end of the bar'may not be lifted vertically but may be only disengaged from the flange 22 by raising the outer end of the bar so as to rock the lug 26 around to permit its withdrawal through the hole 23 in the flange. It is to be understood'that there is suflicient freedom of the pin 25 in the hole 23 to permit this rocking movement. The outer end of the bar .24 curves around downwardly to bear on the top side of the plate It which in the one form here shown is in a plane below that of the top face of the flange 22. The outer end of the bar 24 is radially notched to providea slot 21 into which extends apin 20. By means of the pin 20 extending into this slot 21 the bar 24 is thus normally held against rotation of the pin 25 in the flange 22.

The lateral edges of each bar are in effect serrated with the tooth-like projections blunt on their outer edges and each terminating in the plane of the side of the bar. Preferably the bar The skirt n is provided with a pair of diametrically opposed legs 30 having respectively the out-turned feet 3| and 32, Fig. 1. Connecting rods or bars 33 and 34 respectively pivotally attached by their ends to these feet and carried outwardly. along the pipe ID to have their other ends pivotally interengaged with a yoke bar 35 which is rockably attached to the upper side of the pipe ID. The pivot point of the bar 35 is at its center so that when the bar 35 may be rocked about that central pivot point which is here shown as being formed by the cap screw 36, the rods 33 and 34 are given a reciprocatory motion as indicated by the dash lines, Fig. 1, to in turn cause a corresponding reciprocation of the plate l6 around the flange I4.

Now sincethe collar 2| is held in a stationary position by the sleeve l3 which is also held sta tionary, the inner ends of the respective grate bars 24 are not shifted circumferentially although theouter ends thereof do shift circumferentially as indicated by the dash lines, Fig. 1, where the dash lines indicate the bars as having been shifted to substantially their limit of travel in a counter-clockwise direction. This position is better shown in the detail, Fig. 3, where it is to be noted that there has been a longitudinal movement between opposing faces of adjacent bars 24 so that, for example, a tooth 31 which in the solid line position, Fig; 1, matched up with' the opposing tooth38 on the adjacent bar has been shifted to be opposite the next inner notch at the side of the tooth 38. Of course when the yoke 35 is shifted in the opposite direction, the bars are likewise moved by their outer ends circumferentially as the pins 20 carry the: outer ends of the bars therealong the reversed movement of opposing faces of adjacent bars is obtained whereby the' tooth 31 will thereby be relatively shifted to be on the outer side of the tooth 38. I

Thus it is to be observed that in the relative longitudinal movement of one bar past another, particles of ashes will be worked down through the notches between the teeth and also, clinkers extending between the teeth will be engaged by teeth of the adjacent bar and 7 ground off as the teeth of one bar move past the teeth of the adjacent bar. The occasional upwardly extending teeth 28 aid in causing a better grip to be obtained upon clinkers so as to facilitate the grinding action. The yoke 35 is reciprocated through some suitable mechanism driven by the fuel feed driving motor 39 which through a suitable transmission mechanism causes a relatively slow rotation of .a ratchet wheel 40, Fig. 1, from which extends a pin 4| to engage a connecting rod 42 by one end thereof. This rod 42 has its other end pivotally attached to the yoke 35 whereby the yoke 35 may be reciprocated by the rotation of the wheel 40. Rotation of the wheel 40 is effected by means of the pawl carried by a rocker arm 44 which. is in turn slotted to receive a roller 45 within the slot. This roller 45 is mounted on the wheel 46 which in turn is driven through a reduction gearing by the motor 39. The particular driving mechanism just described is only indicated as being one possible driving means for reciprocating the yoke 35 and the specific form does not enter into my present invention herein described.

In operation, fuel feeds downthrough some suitable means such as a chute 41, Fig. 1, to drop into the feed conductor l0 through which it is caused to travel by some suitable means such as by a ram 48 driven by the motor 39. The fuel is fed through the pipe l0 and discharged upwardly through the sleeve |'3 to have the fuel discharge outwardly on to the'upper sides of the bars. 24. As the bars 24 are given the reciprocatory motion at their outer ends, the fuel will gradually work radially outwardly toward the wall 49 of the combustion chamber. The particular curvature of the bars 24 may be varied in accordance with the fuel to be burned but in any event, the downward curvature at the outer end of each bar is provided so that the ashes and clinkers will be worked radially outwardly and downwardly toward the wall 49. Air for combustion purposes may travel upwardly through the holes I5 and I9 as above indicated. Also the holes I 9. provide surfaces through which the ashes may drop as they fall through between the grate bars.

Referring to Figs. 5 and 6, the same mode of operation may be incorporated in an elongatedgrate structure so as to obtain the same longitudinal shearing action between adjacent grate bar edges. Referring to the modified form, the circular plate I 6 is here shown as being separated into two spaced apart halves 5| and 52 each rockably carried about rounded ends 53 and 54 respectively of a fuel feeding throat 55. These halves 5| and 52 are tied together by the inner links 55 and 57 so as to retain the halves in slidable, rockable contact with the supporting ends 53 and 54. terengaged by their ends so as to permit-the rocking action. Furthermore the outer ends of the halves 5| and 52 are tied together by the links 58 and 59 also pivotally connected therewith. The same grate bars-24 are employed around the circular halves 5| and 52 as in the form above described. Between the circular sections are interposed a sufficient number of parallel side bars 60 to fill in the spaces therebetween with sufiicient freedom to permit the outer ends of these bars 60 to be horizontally reciprocated by pins 6| carried by the links-58 and 59 to enter within the slots provided in the outer ends of the bars. It is to be understood that the inner ends .ofdthe bar 60 are pivotally connected with the the radially disposed bars 24.

Reference is made to my copending application for U. S. Letters Patent for Fuel supply and control system filed May 14,1932, Serial No. 611,285 of which this is a continuation in part. I

Referring to Figs. 2, '7, and 8, I provide means for preventing air from passing up around the outer ends of the grate bars adjacent the refractory lining of the fire bowl in the form of a sectional filler ring generally designated by the numeral 65. This ring is circumferentially expansible so that it may be brought into circumferential contact with the bowl. Each section 66 has an end resting on a depressed end of the adjacent depressed end of the adjacent section 61 to The links 56 and 51 are'pivotally iny be joined thereto by a countersunk headed screw to extending through a tapered slot 89 to screwthreadedly engage the depressed end. The ring 65 is supported by arms I0 carried by a collar Ii mounted on the upturned end of the fuel, pipe l0. There is an arm 10 for each section of theaing which is fixed. to the arm by a countersunk headed screw 12 passing through a tapered radial slot I3 in the section to screw-threadedly engage the arm underneath.

The plate l6 does not bear onthis filler ring 65, but is spaced thereabove slightly so that ash may sift thereunder to fill in on the ring 65 so as to form an air seal to cause the air to pass through between the grate bars removed'from the outer ends to where the clinkers are carried. While I have herein shown and described invention in more or lessminute detail in the form as now best known to me, it is obvious that structural changes may be madewithout departupwardly centrally of the bowl; an annular plate slidably supported by said pipe for horizontal oscillation thereof, the outer portionof the plate being within and adjacent the inner wall of the fire bowl; a collar supported in fixed position about said'pipe; a plurality of radially disposed grate bars resting by their inner ends on said collar and by their outer ends on said plate outer portion; means pivotally interconnecting the'inner ends of the bars to said collar, "said-means being formed to provide for horizontal oscilla tion of the bars about the pivot connections but preventing rotation of the bars about'their axes; pins on said plate slidably engaging the outer ends of said bars to fix the circumferential locations of the bars with respect to said plate; each of said bars being formed with an upper curved face sloping from the pipe upwardly and outwardly and thence downwardly to provide in eflect a flared end for saidpipe means preventing the lifting of the inner ends of saidbars as fuel passes from said pipe over the inner ends of said bars; and means for oscillating said plate, whereby the outer end of each of said bars is horizontally shifted about its inner end asa center and .the longitudinal alignment of adjacent bars is varied.

2. A burner for an underfeed stoker as defined in claim 1 including an adjustable flller ring, and means supported by said pipe for positioning said ring against the inner'wall of said bowl and beneath the outer portion of said plate.

3. A burner for an underfeed stoker as definedin claim 1 characterized by said pipe having an outwardly extending, circumferential flange, and

said plate being slidably carried by said flange.

4; A burner for an underfeed .stoker as defined in claim 1 characterized by said pipe having an outwardly extending circumferential flange, and said plate being slidably carried by said flange,

a skirt extending downwardly from said plateadjacent said flange arid encircling said fuel pipe in spaced relation; said flange having openings therethrough to permit air to travel up within the skirt and discharge through the openings;

said skirt being fixed to said plate; and a pair of arms pivotally connected one each to a diametrically opposite side of the skirt; said reciprocating means being connected to said arms to provide for oscillation of said plate. l

5. A burner for an underfeed stoker as defined in claim 1 characterized by said pipe having an outwardly extending circumferential flange, and said plate being slidably carried by said flange; 1 and a skirt extending downwardly from said plate adjacent said flange and encircling-said fuel pipe in spaced relation: said flange having openings therethrough to permit air to travel up within the skirt and discharge through the openings, whereby an upwardly directed current of air is maintained about said sleeve.

, 6. A burner for an underfeed stoker as defined in claim 1 characterized by said pipe having an -outwardly extending circumferential flange, and said plate being slidably carried by said flange; and a skirt extending downwardly from said plate adjacent said flange and encircling said fuel pipe in spaced relation; said flange having openings therethrough to permit air to travel up within the skirt and discharge through the opening 25 whereby an upwardly directed current of air is maintained about said sleeve; said collar form'- ing the upper end of said pipe and being above said flange.

'7. For an underfeed stoker burner, 'a' gratebar having an upper centrally closed face generally triangular in shape; a pivot pin extending downwardly under the apex, end; and a lip outturned from the outer side of the pin; said bar being formed to have saidface slope upwardly from both apex and base ends to a central portion having a higher elevation than either end form ing in effect a centrally humped bar, said. bar .being notched along its sides to leave laterally extending teeth terminating in the side lines of said face; and some, of said teeth along the portion of the bar which curves ddwnwardly'towardthe bar base having their upper faces above the elevation of the adjacent bar face, the other of said teeth having their upper faces remaining a .the respective face elevations. 8. A burner for an underfeed stoker, comprising in combination with a furnace fire bowl and a. fuelsupply pipe directed to discharge fuel upwardiycentrally of the,bowl; a-plurality of grate ,bars carried within the bowl radiating from around said pipetoward the inner wall of said bowl, said bars each being formed to slope upwardly from said pipe andrthen outwardly and finally abruptly downwardly over their outer ends 5 said bars; whereby a column of fuel discharging upwardly from said pipe may expand outwardly against the inner end portions of said bars as the fuel travels upwardly, the inner end portions of the bars having less'travel than the outer end portions, and ashes and clinkers resulting from combustion of said fuel will be worked outwardly into said pocket to be crushed between said down-'- tumed end portions of said bars and said wall and between adjacent teeth by the relative 1ongitu-, dinal displacement of adjacent bars. FORREST L.-HI'I'CHCOCK. 

